CN103143622B - A kind of medium manufacturing process for improving thick-walled metal pipe fitting forming property - Google Patents

Abstract

The invention relates to a medium forming method for improving the forming performance of thick-walled metal pipe fittings, comprising the following steps: S1, preparing a composite medium: uniformly mixing granular medium with a fusible alloy in a molten state, the melting point of which is lower than that of the pipe The melting temperature of the billet and granular medium; S2, filling the composite medium: pouring the fluid composite medium into the hollow tube blank, and then cooling until the composite medium solidifies; S3, forming the pipe fitting; S4, taking out the medium: allowing the tube to solidify the fusible The alloy transforms into a molten state, causing it to drive the granular media away from the pipe. The invention overcomes the difficulty of achieving better forming quality when traditional rigid molds are used to form thick-walled metal pipe fittings. At the same time, it avoids the multi-step forming of metal pipe parts, greatly saves mold costs, shortens the production cycle, and achieves green and rapid production. purpose of production.

Description

A medium forming method for improving the formability of thick-walled metal pipe fittings

technical field

The invention relates to a plastic forming method for thick-walled metal pipe fittings, more specifically, to a medium forming method for improving the forming performance of thick-walled metal pipe fittings.

Background technique

In the traditional rigid die forming method of metal pipe fittings, due to the hollow feature of the pipe fittings, it is difficult to form at one time, and multiple molds are required, so the cost is high, the production cycle is long, and the pipe fittings are prone to wall thickness reduction, outer wall concave, Defects such as cross-sectional distortion, product quality cannot be guaranteed. In order to avoid or reduce the occurrence of quality defects, mandrels are often used in production or the method of filling pressure-bearing media in pipe fittings. When using a mandrel, more precise process parameters are required, and the cost is high. For filling the pressure medium in the pipe, it is generally divided into two types: flexible medium and solid medium. Flexible medium usually refers to gas and liquid. Generally, liquid such as water or oil is used as the pressure medium, which is commonly referred to as the high-pressure forming technology in the pipe. The pipe is used as the blank, and the pipe blank is pressed into the mold cavity by applying high-pressure liquid inside the pipe. to shape it. However, this method still has certain limitations: ①The cost is high and a high-performance hydraulic pump is required; ②The working pressure is relatively low, generally 0.3-0.5GPa, and it is difficult to boost the pressure; ③Processing thick-walled metal parts or high-strength metal Components (such as titanium alloys, etc.) are limited; ④The mold of the liquid pressure filling process is complex, the production efficiency is low, and it is easy to cause site pollution. Solid media generally include sand, paraffin, rosin, low-melting point alloys, etc., but these fillers have insufficient support for thick-walled pipe fittings or affect production quality.

In recent years, domestic scholars have proposed a new process of forming solid particle media, which uses solid particles instead of flexible media to bulge and form pipes and plates, avoiding the problem of high-pressure liquid sealing. In the Chinese invention patent CN1363434A, a new process of metal pipe solid particle pressure transmission medium bulging is disclosed. Thin-walled metal tube blanks and cup-shaped thin-walled metal tube blanks are bulged, and the obtained parts have smooth surfaces and good quality; but This patent is limited to the bulging process of thin-walled pipes, and the plastic flow capacity of solid particles is insufficient, which easily affects the quality of the inner wall of pipe fittings.

A metal pipe hollow plastic forming forging method disclosed in the Chinese invention patent CN1165717A, the method is to prefabricate a hollow tank-shaped adhesive film that uses PVC or PET as a raw material and is vacuum-injected into the required forged body, and pours it into the plastic film as needed. The liquid filler is mixed with water, iron sand, steel balls, organic starch and other raw materials. After sealing, the core is frozen and hardened at a low temperature between -5°C and -20°C. The core is placed in the metal tube blank and forged together. Finally, the seal is released, and the filling is taken out by melting, softening or crushing the mold core. This method overcomes the obstacle that the hollow forging mold core is difficult to take out, and can be used to make high-strength hollow metal parts. However, the filling process of this method is complicated, the production cycle is long, and it is only suitable for small batch production, and the filling medium used needs to be Hardens at lower temperatures and has a poorer working environment.

Contents of the invention

The technical problem to be solved by the present invention is to provide a medium forming method for improving the forming performance of thick-walled metal pipe fittings.

The technical solution adopted by the present invention to solve the technical problem is to construct a medium forming method for improving the forming performance of thick-walled metal pipe fittings, including the following steps:

S1, preparing composite medium: uniformly mixing the granular medium with the fusible alloy in the molten state, the melting point of the fusible alloy is lower than the melting temperature of the tube blank and the granular medium;

S2, filling the composite medium: pour the fluid composite medium into the hollow tube blank, and then cool until the composite medium solidifies;

S3, formed pipe fittings;

S4, take out the medium: Let the fusible alloy solidified in the tube change into a molten state, so that it drives the granular medium to separate from the pipe.

In the medium forming method for improving the formability of thick-walled metal pipe fittings according to the present invention, in the step S3, the pipe fittings are formed by compression molding, which includes the following steps:

S31, putting the tube blank filled with the composite medium into the mold cavity;

S32, the press drives the upper die to press the tube blank to form a tube fitting.

In the medium forming method for improving the formability of thick-walled metal pipe fittings according to the present invention, the fusible alloy is a bismuth-based low-melting alloy, a tin-based low-melting alloy or a zinc-based low-melting alloy.

In the medium forming method for improving the formability of thick-walled metal pipe fittings according to the present invention, the bismuth-based low-melting point alloy includes the following components, expressed in weight percent:

In the medium forming method for improving the formability of thick-walled metal pipe fittings according to the present invention, the tin-based low-melting point alloy includes the following components, expressed in weight percent:

Sn85.4%

Bi14.6%.

In the medium forming method for improving the formability of thick-walled metal pipe fittings according to the present invention, the zinc-based low-melting point alloy includes the following components, expressed in weight percent:

Zn92.4%

Al4%

Cu3.5%

Mg0.1%.

In the medium forming method for improving the forming performance of thick-walled metal pipe fittings according to the present invention, the granular medium is sand grains or steel balls.

In the medium forming method for improving the formability of thick-walled metal pipe fittings according to the present invention, the range of particle diameter Φ of the granular medium is 2mm≤Φ≤7mm.

In the medium forming method for improving the forming performance of a thick-walled metal pipe according to the present invention, in the step S2, sealing plugs are provided at both ends of the hollow shell.

Implementing the medium forming method for improving the formability of thick-walled metal pipe fittings of the present invention has the following beneficial effects:

1. The pressure-bearing strength of the composite medium is strengthened by solidifying the granular medium with the fusible alloy, so that the hollow pipe has a greater forming limit after filling the medium, and the plastic fluidity of the composite medium is good, which will not affect the forming quality of the inner wall of the pipe . The medium in the tube blank supports the tube wall, which improves the forming performance of thick-walled tube fittings. The wall thickness of the formed parts varies evenly and the tube wall has no depression.

2. When the tube blank is formed, the internal composite medium is in a solid state, so the process of the present invention has very low requirements on sealing. The two ends of the tube blank can use simple sealing plugs or no sealing plugs, which greatly reduces the sealing cost.

3. The method of the present invention can not only process thick-walled pipe fittings with circular cross-section, but also thick-walled pipe fittings with special-shaped cross-sections. For parts with complex shapes, it can be formed at one time, which reduces the cost of molds;

4. The fusible alloy has a low melting point and good fluidity in the molten state. When melting, it can drive the granular medium to be easily poured in and released. The composite medium is easy to manufacture, easy to pour into and discharge from the pipe fittings, and can be used repeatedly. The price of the fusible alloy is low, and the production cost is low.

Description of drawings

The present invention will be further described below in conjunction with accompanying drawing and embodiment, in the accompanying drawing:

Fig. 1 is a schematic cross-sectional view of pipe fitting bending forming in Embodiment 1 of the present invention;

Fig. 2 is a schematic cross-sectional view of a pipe fitting after being bent and formed in Embodiment 1 of the present invention;

Fig. 3 is a schematic cross-sectional view of the flattening and forming of the pipe fitting according to the second embodiment of the present invention;

Fig. 4 is a schematic cross-sectional view of a pipe fitting in Embodiment 2 of the present invention after being flattened;

Fig. 5 is a schematic cross-sectional view of a special-shaped pipe formed by one-time compression molding of the pipe according to Embodiment 3 of the present invention.

detailed description

In order to have a clearer understanding of the technical features, purposes and effects of the present invention, the specific implementation manners of the present invention will now be described in detail with reference to the accompanying drawings.

Implementation Mode 1

This embodiment will be described in detail below with reference to FIG. 1 and FIG. 2 . In this embodiment, the straight pipe billet 2 shown in Fig. 1 is press-formed into the bent pipe fitting 6 shown in Fig. 2. In this embodiment, the straight pipe billet 2 is an aluminum alloy 6061-T651 with a yield strength of 275 MPa, and the melting point range is 580-650°C, the diameter of the tube blank 2 is 76mm, and the wall thickness is 6mm.

For thick-walled metal pipes such as aluminum alloys and magnesium alloys with low strength, the requirements for the compression resistance of the composite medium 3 filled in the pipes are not high, and bismuth-based or tin-based low-melting point alloys can be used as fusible alloys. The bismuth-based low melting point alloy includes 50.6% Bi, 26.9% Pb, 12.5% Sn, and 10% Cd, with a strength of 42.1MPa and a melting point of 70°C. The tin-based low melting point alloy includes 85.4% Sn, 14.6% Bi, its strength is 85MPa, and its melting point is 190°C. In this embodiment, a bismuth-based alloy with a low melting point is selected.

Sand grains or steel balls can be used as the granular medium. The particle size of the granular medium Φ ranges from 2mm≤Φ≤7mm. Under the premise of ensuring the supporting force, it has good fluidity and avoids damage to the inner wall of the pipe during molding. In this embodiment, steel balls with a diameter of 4 mm are used. Evenly mixing the fusible alloy with steel balls can improve the compression resistance.

Referring to Figure 1, the bending forming device includes an upper mold cavity 1, a tube blank 2, a composite medium 3, a lower mold cavity 4 and a sealing plug 5, with the center line of the tube blank 2 as the parting surface, and the upper mold cavity 1 for the bending of the pipe fitting 6 The outer contour of the inner side, the lower mold cavity 2 is the outer contour of the curved outer side of the pipe fitting 6 .

The forming steps are as follows:

S1, uniformly mixing the fusible alloy and steel balls at a ratio of 1:1 to form a composite medium 3; the ratio between the fusible alloy and steel balls can be adjusted according to the material and wall thickness of the tube blank 2;

S2, seal one end of the tube blank 2 with the sealing plug 5, pour the composite medium 3 in molten state into the tube blank 2 sealed at one end, then seal the other end of the tube blank 2 with the sealing plug 5, and let it cool until the composite medium 3 solidifies The composite medium 3 in molten state means that the fusible alloy is in a molten state, and the steel ball is not melted;

S3, forming the pipe fitting 6, specifically includes step S31: placing the tube blank 2 on the lower mold cavity 4, and step S32: the press drives the upper mold cavity 1 to press and form the tube blank 2;

S4, after the pipe blank 2 is formed into the pipe fitting 6, the sealing plug 5 is pulled out, and a temperature higher than the melting point of the eutectic alloy is applied to the pipe fitting 6, so that the composite medium 3 is separated from the pipe fitting 6, and the composite medium 3 can be recycled.

In this embodiment, the compression molding method is used to form the pipe fitting 6 , but it is only a preferred embodiment, and the pipe fitting 6 can also be formed by other methods such as rolling and numerically controlled pipe bending.

Implementation mode two

This embodiment will be described in detail below with reference to FIG. 3 and FIG. 4 . In this embodiment, the 35# carbon steel pipe with high strength is used, the yield strength is 315MPa, the diameter-thickness ratio is 12.8, and the steel pipe with the diameter-thickness ratio less than 20 is called a thick-walled pipe, which requires a composite medium that can withstand relatively high pressure. .

In this embodiment, steel balls with a diameter of 4 mm are solidified with a zinc-based low-melting point alloy, and the two are uniformly mixed at a ratio of 1:1. The zinc-based low melting point alloy includes 92.4%Zn, 4%Al, 3.5%Cu, 0.1%Mg, with a strength of 194MPa and a melting point of 380°C.

In this embodiment, the straight tube blank 2 shown in FIG. 3 is press-formed into the square tube fitting 6 shown in FIG. The tube blank 2 is flattened from a circular section to a square section, the hollow volume in the tube decreases, and the composite medium 3 filled in the tube will undergo plastic flow and be extruded, but the small steel balls mixed in the composite medium 3 can reduce the volume of the composite medium to a certain extent. 3's plastic flow ability, so the composite medium 3 can also play a better role in bearing pressure and avoid defects.

The forming steps are as follows:

S1, uniformly mixing fusible alloy and steel ball at a ratio of 1:1 to form composite medium 3;

S2, pour the composite medium 3 in molten state into the tube blank 2, and let it stand for cooling until the composite medium 3 is solidified;

S3, forming the pipe fitting 6, specifically includes step S31: placing the tube blank 2 on the lower mold cavity 4, and step S32: the press drives the upper mold cavity 1 to flatten the tube blank 2;

S4, after the pipe blank 2 is formed into the pipe fitting 6, a temperature higher than the melting point of the eutectic alloy is applied to the pipe fitting 6, so that the composite medium 3 is separated from the pipe fitting 6, and the composite medium 3 can be recycled.

Implementation Mode Three

This embodiment will be described in detail below with reference to FIG. 5 . The difference between this embodiment and Embodiment 1 and Embodiment 2 is that the processing steps of the parts are reduced, that is, two bendings and partial flattening are completed at one time, and the manufactured pipe fitting 6 is a special-shaped cross-section pipe, and the cross-sectional shape includes: Round, square and oval. The method of the present invention is applicable to any pipe 6 whose cross-section is a closed curve profile shape. In this embodiment, the properties of the material of the tube blank 2 and the composite medium 3 filled therein are the same as those in the first embodiment. Referring to FIG. 5 , the forming device includes a tube blank 2 , an upper mold cavity 1 , a lower mold cavity 4 , a composite medium 3 and a sealing plug 5 .

The forming steps are as follows:

S1, uniformly mixing fusible alloy and steel ball at a ratio of 1:1 to form composite medium 3;

S2, seal one end of the tube blank 2 with the sealing plug 5, pour the composite medium 3 in molten state into the tube blank 2 sealed at one end, then seal the other end of the tube blank 2 with the sealing plug 5, and let it cool until the composite medium 3 solidifies ;

S3, forming the pipe fitting 6, specifically includes step S31: placing the tube blank 2 on the lower mold cavity 4, and step S32: the press drives the upper mold cavity 1 to bend and flatten the tube blank 2;

S4, after the pipe blank 2 is formed into the pipe fitting 6, the sealing plug 5 is pulled out, and a temperature higher than the melting point of the eutectic alloy is applied to the pipe fitting 6, so that the composite medium 3 is separated from the pipe fitting 6, and the composite medium 3 can be recycled.

Embodiments of the present invention have been described above in conjunction with the accompanying drawings, but the present invention is not limited to the above-mentioned specific implementations, and the above-mentioned specific implementations are only illustrative, rather than restrictive, and those of ordinary skill in the art will Under the enlightenment of the present invention, many forms can also be made without departing from the gist of the present invention and the protection scope of the claims, and these all belong to the protection of the present invention.

Claims (4)

1. A medium forming method for improving the formability of thick-walled metal pipe fittings, characterized in that, comprising the following steps: S1, preparation of composite medium: uniformly mix the granular medium with the fusible alloy in the molten state, the melting point of the fusible alloy is lower than the melting temperature of the tube billet and the granular medium; the fusible alloy is a bismuth-based low-melting alloy, a tin-based low-melting alloy Melting point alloy or zinc-based low melting point alloy; the granular medium is sand grains or steel balls; The bismuth-based low melting point alloy includes the following components, expressed in weight percent: 50.6% Bi, 26.9% Pb, Sn12.5%, Cd10%; The tin-based low melting point alloy includes the following components, expressed in weight percentage: Sn85.4%, Bi14.6%; The zinc-based low melting point alloy includes the following components, expressed in weight percent: Zn92.4%, Al4%, Cu3.5%, Mg0.1%; S2, filling the composite medium: pour the fluid composite medium into the hollow tube blank, and then cool until the composite medium solidifies; S3, formed pipe fittings; S4, take out the medium: Let the fusible alloy solidified in the tube change into a molten state, so that it drives the granular medium to separate from the pipe. 2. The medium forming method for improving the formability of thick-walled metal pipe fittings according to claim 1, characterized in that, in the step S3, the pipe fittings are formed by compression molding, which includes the following steps: S31, putting the tube blank filled with the composite medium into the mold cavity; S32, the press drives the upper die to press the tube blank to form a tube fitting. 3. The medium forming method for improving the formability of thick-walled metal pipe fittings according to claim 1, characterized in that the range of the particle diameter Φ of the granular medium is 2mm≤Φ≤7mm. 4. The medium forming method for improving the formability of thick-walled metal pipes according to claim 1, characterized in that, in the step S2, sealing plugs are provided at both ends of the hollow shell.